[libc-commits] [libc] [libc] Fix usage of std::nullptr_t in LibcTest.h. (PR #114321)

[via libc-commits]

lntue wrote:

> Consider including what you use
> 
> libc/src/__support/CPP/type_traits/is_null_pointer.h

All headers inside `src/__support/CPP/type_traits/*` are included in `src/__support/CPP/type_traits.h`, which is included at the beginning of the file, and I don't think we want to include individual type trait headers.  That being said, we should have `nullptr_t.h` header separated somewhere, and not included inside `type_traits/is_null_pointer.h`.

https://github.com/llvm/llvm-project/pull/114321